As a conventional technique, a bowl-shaped recess is formed in a cylindrical structure arranged to surround a high voltage cable, and a partial discharge sensor formed in an inverted cone shape is arranged in the bowl-shaped recess (see Patent Document 1).
In order to detect a partial discharge within a GIS, in general, a sensor is required to receive broadband radio-frequency waves of 500 MHz to 1500 MHz generated during the partial discharge.
On the other hand, when an inverted cone shaped antenna is arranged on a planar ground, similar characteristics to those of a disk cone antenna having broadband characteristics can be obtained.
In the conventional partial discharge sensor, a place of the cylindrical structure where the inverted cone shaped partial discharge sensor is to be arranged is formed in a bowl shape, and a surface of the structure is set to a ground potential to be thus approximated to a planar ground, and therefore similar broadband characteristics to those of a disk cone antenna are obtained. prevented.